Films of metals and metal oxides, particularly ruthenium and osmium films and oxides thereof, are becoming important for a variety of electronic and electrochemical applications. For example, high quality RuO2 thin films deposited on silicon wafers have recently gained interest for use in ferroelectric memories. Ruthenium and osmium films are generally unreactive to silicon and metal oxides, resistant to diffusion of oxygen and silicon, and are good conductors. Oxides of these metals also possess these properties, although perhaps to a different extent.
Thus, films of ruthenium and osmium and oxides thereof have suitable properties for a variety of uses in integrated circuits. For example, they can be used in integrated circuits for electrical contacts. They are particularly suitable for use as barrier layers between the dielectric material and the silicon substrate in memory devices, such as ferroelectric memories. Furthermore, they may even be suitable as the plate (i.e., electrode) itself in capacitors.
There are a wide variety of ruthenium and osmium compounds that can be used as precursors for the preparation of such films. Many are particularly well suited for use in chemical vapor deposition techniques. See, for example, U.S. Pat. No. 5,372,849 (McCormick et al.), which discloses the use of ruthenium and osmium compounds containing carbonyl ligands and other ligands. Typically, such compounds can be prepared by the thermal or photolytic reaction of Ru3(CO)12 or Os3(CO)12 with a neutral two electron donor ligand in benzene. See, for example, Johnson et al., Nature, 901-902 (1967), and Cowles et al., Chem. Commun., 392 (1969). Although such reactions provide good yields (e.g., 80-90%), they require generally long reaction times (e.g., 4 days). Thus, there is a continuing need for methods for the preparation of such ruthenium and osmium compounds in high yields with shorter reaction times.